1. Field of the Invention
The present invention relates generally to a system and method for a high altitude reconnaissance vehicle (HARVe).
2. Description of the Related Art
Whether for military or civilian use, atmospheric based vehicles or stations are becoming more commonplace in a society requiring real-time communications and information to be supplied over greater distances. Systems placed in low, medium and high altitude locations include weather balloons, satellites used for reconnaissance or communications, and systems for environmental analysis, to name a few. The existing atmospheric based systems include sensing devices from infrared (IR) and radio frequency (RF) devices, advanced optical devices, each having differing capabilities to detect and/or relay valuable information. Several factors are taken into consideration when designing and deploying these systems. Among these factors are ease of deployment, time required to deploy, altitude requirements, environmental factors the systems are exposed to during both initial deployment and final location, costs, and especially in military applications, vulnerability to ground attack. Each of these factors is weighed during initial design and conception stages.
Existing atmospheric based systems are generally classified into an unmanned air vehicle (UAV), an ultra long-duration balloon (ULDB), a commercial telecommunications balloon (CTB), a high altitude long endurance (HALE) remotely operated aircraft (ROA), and a near-space maneuvering vehicle (NSMV). Each has unique operating altitudes, payload capabilities, ranges, time to deployment, reconnaissance coverage areas, and station-keeping (i.e. remaining relatively stationary at its deployed position) and other characteristics. The UAV has a maximum altitude of about 65,000 feet, a payload of about 2000 pounds, a range of about 3000 nautical miles, a deployment time of more than 24 hours, and a coverage area of roughly 40,000 nautical square miles in a 24 hour period at a 1 m resolution and up to 1900 spot images per mission at 0.3 m resolution. ULDBs are deployed at an altitude of about 110 to 120 kft (kilo feet), can remain deployed for up to 100 days, have a payload capacity of about 6000 lbs., can circumnavigate the earth, and require tether for station-keeping at an altitude of about 60 kft. CTBs are currently licensed by the Federal Communications Commission, are deployed at about 100 kft, and have a coverage area of about the size of Oklahoma. HALE ROA are deployed at about 60,000 feet, can remain aloft for potentially weeks to months at a time, carry a maximum payload of about 200 kg, and can be deployed as both station-keeping and moving over large areas. Finally, NSMVs can ascend to about 120,000 ft, have a range of about 200 nautical miles, can station-keep for about 5 days, can carry a payload of about 100 lbs., consume about 50 Watts of power, but have not successfully flown under propeller power for station-keeping.
The present near-space platforms have a number of disadvantages. UAVs require multiple vehicles to provide continuous, persistent coverage. They also require a support ground crew and its infrastructure. UAVs are also vulnerable to air defenses due to their low altitude and can be grounded by bad weather. ULDBs also have problems. Without propulsion, the ULDBs are unable to station-keep and depend on wind direction for movement. Thus, to station keep they require tethering. With a propulsion system, the ULDBs require periodic refueling and move slowly between the launch area and the on-station location. If manned, the ULDBs need to fly low enough, contain a pressurized cabin or wear masks to provide oxygen for the crew allowing them to be targets to air defenses.
Satellites are also utilized for reconnaissance. Satellites have a different set of problems. Low-earth orbit satellites are only on-station over a particular location for short periods of time. During these short periods, there are a number of competing demands for their resources. Geosynchronous satellites are much further away, requiring more sophisticated optics and electronics to bridge the distance. The lead-time for new satellites is many years, making new satellites unavailable to support short-term needs.
Some of the additional disadvantages associated with present atmospheric based systems include the following. Winged aircraft and most lighter-than-air airships, or tethered aerostats are limited to the lower altitudes with denser atmosphere, thereby limiting their horizon coverage. Further, they require substantial support and are not generally on station for long periods (days or months) due to crew limits, weather vulnerability, and/or equipment reliability. Satellites are expensive to deploy and, although their horizon coverage is great, their distance to the objects of surveillance, and communications relays, combined with on-board power constraints limit resolution, detectibility, and communications bandwidth. Also, a single satellite cannot provide continuous reconnaissance because a platform in low-earth orbit passes outside of the field of view of a target within about ten minutes and does not return for at least one orbit period of about 90 minutes. A geosynchronous-orbit satellite could in theory provide continuous reconnaissance but at enormous cost because of the expensive sensors required for the very long distance to geosynchronous orbit (over 22,000 miles). A constellation of low-earth-orbit satellites could also provide continuous reconnaissance but again at enormous cost because of the significant number of satellites required.